R33 Lean At Idle

[Mickroy]

I've posted a few threads on my r33 over the past two years, and the issue is still not sorted. Symptoms at present are a shocking idle that jumps all over the place, tries to stall, etc. Secondly, according to my boost guage the manifold vaccum is down. It sits at about 12, when it should be closer to 20.

Now, I have had this car looked at by multiple workshops, spent enough money to buy a new turbo, and swap tested just about everything bar the engine!! I'm deadset on the brink of getting a halfcut & swapping out the engine. It simply doesnt have enough fuel down low, and i dont know why... i have an untuned power fc, but i want the car to run well on the stock ecu before i get the thing in there. However, i use it for testing. If i dial in as much fuel as i can at idle then the car will idle nicely... and i mean as much as i can, as in the car should stall! With stock ecu the idle never stabalises... you can smell how lean it is, and if i hook it up to nissan datascan you can see the zero reading from the o2 sensor. Soon as i lift the accelerator off idle it starts to cycle. I have read every single thread on unstable idles, lean idles, etc, etc , and nothing has helped.

I've listed as much of the stuff i've dont as i can remember, so any advice on different things i could try would be appreciated. It's only been recently that ive noticed the low vaccum pressure... i think it's telling a big story.

What I've done

Cleaned ACC valve, swap tested AFM, TPS, O2, & Coolant sensors, swap tested ecu, ecu diagnostics, new battery, checked ignition timing, scoured for vaccum leak, changed plugs, gapped plugs, sealed up coils incase of cracking, changed fuel filter, checked fuel pressure, checked timing belt markings, replaced timing belt coz it was a touch loose, had injectors cleaned, checked compression (150psi across all 6)... thats all i can think of at the moment, but im sure theres more.

Cheers,

mick

[paulr33]

do powerfc factory reset (youll loose all tune data)

ETC, DATA INIT

choose yes

power car off

turn car to ACC

turn off boost kit, ETC, FUNCTION SELECT

power car on

let it idle for 10 mintes (dont touch a thing)

turn on demister

let it idle for 10 minutes

turn on aircon

let it idle for 10 minutes

make sure idle is stable

turn car off

turn car on

see if idle is stable

if its not, post up what you have under SENSOR SW CHECK

[AzzurrA]

honestly mate, from the way you've described that (running lean, idling badly etc) it sounds like you have an air leak somewhere...

you've checked all your intercooler clamps etc?

checked that a vacuum line hasn't been left off by mistake or something?

[Mickroy]

do powerfc factory reset (youll loose all tune data)

ETC, DATA INIT

choose yes

power car off

turn car to ACC

turn off boost kit, ETC, FUNCTION SELECT

power car on

let it idle for 10 mintes (dont touch a thing)

turn on demister

let it idle for 10 minutes

turn on aircon

let it idle for 10 minutes

make sure idle is stable

turn car off

turn car on

see if idle is stable

if its not, post up what you have under SENSOR SW CHECK

Have done this when i first got it... also checked everything sensor wise, nothing is out of whack, cept for what the o2 sensor sees, but ive tried 4 o2 sensors so i know it's only telling what it sees and isnt faulty.

[Mickroy]

honestly mate, from the way you've described that (running lean, idling badly etc) it sounds like you have an air leak somewhere...

you've checked all your intercooler clamps etc?

checked that a vacuum line hasn't been left off by mistake or something?

I hear that, and believe me, i have looked.... been over every clamp, every hose, sprayed around everywhere with soapy water & carby cleaner... if there is one, i cant find the prick!

[AzzurrA]

okay, another question: is it still lean higher in the revs?

[Mickroy]

No, mega-rich like a stock ecu skyline should be... soon as its off idle its fine - have confirmed this with external wideband sensor.

[R31Nismoid]

Its possible after checking something, it was ok... and later on it wasnt.

So you possibly had one problem, fixed that and another arose from something already checked.

Just a possibility.

Is the car stock?

Where are you located and what specialist skyline workshops have you visted?

[rob82]

Sounds like all the sysptoms of a vaccum leak. Check over all the pipes twice over esspecially around the condulated rubber angle pipes and also where the piping goes through the engine bay. Also check crankcase ventillation system is sealed.

[Mickroy]

Its possible after checking something, it was ok... and later on it wasnt.

So you possibly had one problem, fixed that and another arose from something already checked.

Just a possibility.

Is the car stock?

Where are you located and what specialist skyline workshops have you visted?

You may actually be right. It seems that over time the issue has *evolved*. It has changed symptoms, but the car has never been right. Not much done to the car... exhaust, front mount, intake, thats about it. Unfortunately no pro skyline shop in north qld mate.

To those who suggest vac leak, that is the front runner in my books too. I will thoroughly check this weekend & post back my findings. I suspect somewhere around the intake manifold.

cheers.